Nguyen Xuan Thanh Tram, Kunio Ishikawa, Fabrication of calcite block with interconnecting porous structure for bone substitutes, 6th International Conference on the Development of Biomedical Engineering in Vietnam, BME 2016, 2018.01, In this study porous calcite block was fabricated using calcium hydroxide (Ca(OH)2) as precursor and wax spheres as pore-creating volatile particles. X-ray diffraction (XRD) and Scanning electron microscope (SEM) were used to characterize phase composition and structure. The results indicated that pure calcite block consisting of interconnecting pores with pore size about 200–400-µm diameter could be obtained. It is indicated that wax spheres are advantageous on producing interconnecting porous structure since they could be easily removed by sintering. Porous calcite block with interconnecting porous structure is expected to apply as bone substitutes since it could support effectively bone cell activities to promote bone healing..

8.

Arief Cahyanto, Kanji Tsuru, Kunio Ishikawa, Masanori Kikuchi, Mechanical strength improvement of apatite cement using hydroxyapatite/collagen nanocomposite, 28th Annual Meeting of the International Society for Ceramics in Medicine, Bioceramics 2016, 2017, The combination of tetracalcium phosphate (TTCP; Ca4(PO4)2O) and dicalcium phosphate anhydrous (DCPA; CaHPO4) which are known as one system of apatite cements already used in the medical and dental application. In spite of several advantages of apatite cements, such as self-setting ability and biocompatibility, their mechanical strengths are still low. The aim of this study is to improve the mechanical strength of the TTCP-DCPA apatite cement using the hydroxyapatite/collagen nanocomposite (HAp/Col). The apatite cement powder was prepared using an equimolar TTCP and DCPA with addition of 10% and 20% of the HAp/Col. That without the HAp/Col was used as a control group. Each group was mixed with 1 mol/L Na1.8H1.2PO4 aqueous solution at powder/liquid ratio of 0.5 and hardened at 37°C and 100 % of relative humidity for 24 hours. A setting time of the cement was evaluated using Vicat needle according to ISO 1566 for dental zinc phosphate cements. Morphology of the cements set were observed by the scanning electron microscopy (SEM), and crystalline phases were identified by the powder X-Ray diffractometry (XRD). The mechanical strength of the cement set was evaluated by the diametral tensile strength (DTS). The setting times of cements were the shortest for the cement with HAp/Col and the longest for the control. XRD patterns of the cement at 24 hours after mixing revealed that all cements changed into apatite from the mixture of TTCP and DCPA. The DTSs of cements were the highest for the cement with 20% HAp/Col and the lowest for the control with significant differences between the cement with 20 % HAp/Col and respective other two cements. The scanning electron micrographs of the surface and fracture surface of the cements suggested that the cement with HAp/Col showed denser structure in comparison to the control and the HAp/Col fibers and/or sheets covered the fracture surface. The HAp/Col would act as reinforcement fibers as well as an adhesive of apatite granules formed by the reaction between TTCP and DCPA. The setting time and mechanical strength of apatite cement was statistically significant improved by adding 20% HAp/Col..

Ishikawa Kunio, Fabrication of carbonate apatite based on dissolution-precipitation reaction using precursors., The 28th Symposium & Annual Meeting of the International Society for Ceramics in Medicine, 2016.10.

C. Sunarso, Riki Toita, Kanji Tsuru, Kunio Ishikawa, Increased pre-osteoblast bioactivity on ca-modified titanium, 27th Symposium and Annual Meeting of the International Society for Ceramics in Medicine, 2015, 2016, The aim of this study is to evaluate a new and simple titanium surface modification by calcium treatment. The treatment was carried out by immersing titanium in CaCl2 solution at 80oC. The XPS spectra showed that calcium has been successfully immobilized onto titanium surface. Moreover, the thickness of oxide layer increased after the treatment due to exposure of titanium surface to aqueous solution. In vitro evaluation revealed that the calcium treated titanium shows cytocompatibility including greater cell attachment and proliferation. The results suggested that our current titanium surface modification is promising to improve osteoconductivity..

26.

Nguyen Xuan Thanh Tram, Michito Maruta, Kanji Tusru, Shigeki Matsuya, Kunio Ishikawa, Osteoconductivity and bioresorption of an interconnecting porous carbonate apatite with enhanced mechanical strength, 27th Symposium and Annual Meeting of the International Society for Ceramics in Medicine, 2015, 2016, We have established a processing method to fabricate three-dimensional porous carbonate apatite (CO3Ap) with interconnected porous structure and improved mechanical strength. Briefly, porous CO3Ap materials were produced via phosphorization of porous calcite precursor in hydrothermal condition. In order to make porous calcite precursor, negative replication of modified polyurethane foam template was conducted. In this study, an in vivo behavior of that porous CO3Ap was evaluated. The interconnected porous CO3Ap material was implanted in the tibia of Japanese male rabbits and removed after a period of 6 months. Micro-computed tomography (μ-CT) scanner and histological analysis were used to characterize the bone formation response of the porous CO3Ap. The results suggest that porous CO3Ap with enhanced mechanical strength was not only osteoconductive but also bioresorbable therefore it could be used as bone substitute material..

27.

Tya Indah Arifta, M. L. Munar, K. Tsuru, Kunio Ishikawa, Preparation of Porous α-TCP by Fusion of DCPD Coated α-TCP Spheres, 27th Symposium and Annual Meeting of the International Society for Ceramics in Medicine, 2015, 2016, The aim of present study was to fabricate porous α-Tricalcium phosphate (α-TCP) with adequate mechanical strength and pore interconnectivity. First step, α-TCP spheres were exposed to acidic calcium phosphate solution to allow growth and interlocking of dicalcium phosphate dihydrate (DCPD) crystals precipitated on the surface of the α-TCP spheres. Then, the DCPDcoated α-TCP spheres were sintered at 1,500°C for 6h, which resulted in the fusion of spheres to form the interconnected porous block. XRD analysis showed single phase α-TCP was obtained. Mechanical strength of porous α-TCP was 6.9 ± 1.6 MPa and porosity was 53 ± 5%. The obtained porous α-TCP could be employed as potential bone substitute or precursor for other bioceramics like carbonate apatite and hydroxyapatite..

28.

Khairul Anuar Shariff, Kanji Tsuru, Kunio Ishikawa, Regulation of DCPD formation on β-TCP granular surface by exposing different concentration of acidic calcium phosphate solution, 27th Symposium and Annual Meeting of the International Society for Ceramics in Medicine, 2015, 2016, Regulation of DCPD formation on β-TCP granules was achieved by exposing β-TCP granular with different concentration of acidic calcium phosphate solution. It was found that a higher amount of DCPD was formed when exposed β-TCP granular with the higher concentration of acidic calcium phosphate solution. Morphological observation shows that the surface of β-TCP granular was fully coated with DCPD crystals after exposed to the higher concentration of acidic calcium phosphate solution. These results demonstrated that the DCPD formation on the β-TCP granular surface could be regulated by varying the concentration of acidic calcium phosphate solution..

29.

Arief Cahyanto, Kanji Tsuru, Kunio Ishikawa, Transformation of apatite cement to B-Type carbonate apatite using different atmosphere, 27th Symposium and Annual Meeting of the International Society for Ceramics in Medicine, 2015, 2016, Apatite cement (AC) is a breakthrough in biomaterials for the reconstruction of the bone defect. However, the replacement of AC to bone up to the present time is still controversial for researchers. Several researchers have reported that AC was replaced by bone while others claimed replacement was limited. The aim of this study is to investigate the transformation mechanism of AC to B-Type carbonate apatite (CO3Ap) using different atmosphere. An in vitro study mimicking the body environment was employed in order to examine the effect of setting atmosphere on the composition of set AC. An equimolar of tetracalcium phosphate (TTCP; Ca4 (PO4)2O) and dicalcium phosphate anhydrous (DCPA; CaHPO4) mixed with distilled water was enabled to harden at 37°C and 100% of relative humidity under presence of 5% CO2, 100% CO2, and 100% N2 atmospheres. XRD and FT-IR analyses revealed that in the presence of 100% CO2 and 5% CO2, Btype CO3Ap could be determined and only small amounts of TTCP remained unreacted. On the contrary, in the presence of 100% N2, the CO3-2 bands could not be detected and larger amount of TTCP remained unreacted compared to 5% CO2 and 100% CO2 atmospheres. SEM morphology showed that the microstructure of AC was entangled and locked to each other. In addition, the small needle like crystals appeared in the surface of 100% N2, similar to hydroxyapatite. We concluded that the CO3-2 ions incorporated in AC during setting reaction may be one of the essential factors for CO3Ap formation..

Ishikawa Kunio, Carbonate apatite for bone regeneration: An insight to the future development, 27th Symposium and Annual Meeting of the International Society for Ceramics in Medicine, 2015.10.

33.

Ishikawa Kunio, Arief Cahyanto, Kanji Tsuru, Transformation of apatite cement to B-type carbonate apatite using different atomosphere, 27th Symposium and Annual Meeting of the International Society for Ceramics in Medicine, 2015.10.

34.

Ishikawa Kunio, Yuki Sugiura, Kanji Tsuru, Carbonate apatite foam fabricated from α-TCP foam granuels through hydrotheremal treatment with various amount of NaHCO3, 27th Symposium and Annual Meeting of the International Society for Ceramics in Medicine, 2015.10.

Pham Trung Kien, Tsuru Kanji, Kunio Ishikawa, Development and characterization of porous calcium phosphate cement using α-tricalcium phosphate bead, 5th International Conference on the Development of Biomedical Engineering, 2014, 2015, Interconnected set porous-calcium phosphate cement (set porous-CPC), which has fully interconnected pores could be an ideal bone substitute. In this study, set porous- CPC consisting of α-tricalcium phosphate (α-TCP) beads and acidic calcium phosphate solution was developed and its basic setting reaction was studied. When α-TCP beads were exposed to the acidic calcium phosphate solution, brushite (CaHPO4 ·2H2O) was formed on the surface of the α-TCP beads. The formed brushite crystals interlocked with each other, resulting in a setting reaction of α-TCP microspheres within 10 min at 37°C. As a result of this setting reaction, a fullyinterconnected calcium phosphate macroporous structure was obtained. The set porous-CPC were immersed into simulated body fluid (SBF) at 37oC for different immersion time, The result clearly showed that brushite surface layer transformed to apatite layer after 3 days immersion into SBF solution by dissolution-precipitation reaction. Since apatite layer show excellent tissue response, the set porous-CPC would be a promising biomaterial used as artificial bone substitutes, and as the scaffold for tissue engineering..

46.

Arief Cahyanto, Riki Toita, Kanji Tsuru, Kunio Ishikawa, Effect of particle size on carbonate apatite cement properties consisting of calcite (Or vaterite) and dicalcium phosphate anhydrous, 26th Symposium and Annual Meeting of the International Society for Ceramics in Medicine, ISCM 2014, 2015, Calcium carbonate (CaCO3) has been known as one of the components of carbonate apatite (CO3Ap) cement. Calcite is one of the polymorph of CaCO3 with big particle size and excellent stability. In contrast, vaterite has small particle size and a metastable phase. To discover the effect of particle size on the properties of CO3Ap cement, this study investigated the different particle size of vaterite; calcite from vaterite, which has almost similar particle size and shape with vaterite; grounded calcite and ungrounded calcite. The powder phase of calcite or vaterite combined with dicalcium phosphate anhydrous (DCPA) was mixed with 0.8 mol/L of Na2HPO4 solution in 0.45 liquid to powder ratio. The paste was packed into a split stainless steel mold, covered with glass slide and kept at 37°C and 100% relative humidity for a period of time. XRD and FT-IR analysis revealed that CO3Ap cement consisted of vaterite and DCPA transformed to pure B-type CO3Ap in 72 hours while CO3Ap cement that consisted of calcite with different particle size was not completely transformed to CO3Ap even until 240 hours. We concluded that CO3Ap cement consisted of vaterite with small particle size and metastable phase properties is more effective as starting material due to its fast transformation to CO3Ap..

Thi Bang Le, Xing Ling Shi, Kunio Ishikawa, Radzali Othman, Bone marrow cell response on carbonate apatite/PCL-coated α-tricalcium phosphate foam, 5th Regional Conference on Materials Engineering and the 5th Regional Conference on Natural Resources and Materials 2013, RCM5 and RCNRM5 2013, 2014, The aim of this research work was to investigate in vitro effect of the carbonate apatite/poly(ε- caprolactone) (CO3Ap/PCL) on α-tricalcium phosphate (α-TCP) foam. α-TCP was produced by sintering CaCO3 and CaHPO4•2H2O at 1500°C for 5 h. It was then coated with CO3Ap/PCL (wt/wt=1/3) to improve both mechanical and biological properties. The initial cell attachment and proliferation of the bone marrow cells were carried out on the α-TCP and CO3Ap/PCL-coated α- TCP foams. The cell proliferation was calculated by AlamarBlue assay. The cells were able to migrate and proliferate well on both α-TCP and CO3Ap/PCL-coated α-TCP foams indicating an excellent biocompatibility. The incorporation of CO3Ap on the coating layer improved cellular attachment and accelerated proliferation. Thus, CO3Ap/PCL-coated α-TCP foam might be a promising candidate as implant material..

68.

N. X T Tram, M. Maruta, K. Tsuru, S. Matsuya, Kunio Ishikawa, Hydrothermal conversion of calcite foam to carbonate apatite, Advances in Bioceramics and Porous Ceramics VI - 37th International Conference on Advanced Ceramics and Composites, ICACC 2013, 2014, We have previously reported an inverse ceramic foam method aiming to improve mechanical strength of calcite foam that has interconnected porous structure. The modified foam was obtained by multiple Polyurethane coating. In previous study, calcium hydroxide (Ca(OH)2) slurry was poured into the foam. After drying, the foam was burnt out to remove polyurethane and to carbonate Ca(OH)2 under mixed O2-CO2 atmosphere. Ca(OH)2 was completely converted to calcite. Those calcite foams are the useful precursors for the preparation of the three-dimensional (3D) interconnected porous carbonate apatite (CO 3AP) foam. Therefore, we investigated the hydrothermal treatment of calcite foam to CO3AP foam in phosphate solution. The results indicated that the conversion ratio depends on the degree of porosity of calcite precursor and calcite foam was completely transformed to CO3Ap foam at 100°C for 14 days. The CO3AP foam showed the increase in the compressive strength compared to conventional foam. So, it is concluded that CO3Ap foam fabricated in this study could be a good candidate for the bone replacement material in clinical application..

69.

Tram Nguyen Xuan Thanh, Michito Maruta, Kanji Tsuru, Shigeki Matsuya, Kunio Ishikawa, Three-dimensional porous carbonate apatite with sufficient mechanical strength as a bone substitute material, 11th International Fatigue Congress, FATIGUE 2014, 2014, In this study, three-dimensional porous carbonate apatite (CO3Ap) materials with the chemical compositions and structures similar to cancellous bone were produced via phosphorization of porous calcite precursor in hydrothermal condition. In order to make porous calcite precursor, negative replication of polyurethane foam that named as inverse ceramic foam method was conducted. When the polyurethane template occupied within the ceramic solid walls disappeared due to burning at high temperature, interconnected hollow pathways were produced. Polyurethane foam was used as a porogen-template firstly was coated layer by layer with synthetic resin to modify morphology and enlarge thickness of struts so as to expand porous area for satisficing cellular bioactivities. Calcium hydroxide (Ca(OH)2) slurry was then infiltrated into resin coatedpolyurethane foam. Heat treatment in atmosphere of oxygen and carbon dioxide gases was carried out to eliminate polyurethane template and induce carbonation process. Ca(OH)2 was converted to calcite with the internal porous channel architecture simulating polyurethane foam struts network. That interconnected porous calcite was subsequently transformed to CO3Ap with remaining the same macroporous structure through hydrothermal treatment in phosphate solution. The porous CO3Ap materials were implanted in the tibia of Japanese male rabbits and removed after a period of 3 months. The bone formation response of the three-dimensional porous carbonate apatite in vivo has been preliminary studied using micro-computed tomography (μ-CT) scanner. The results showed that the porous implant materials have sufficient mechanical strength to provide structural support during bone remodeling and successfully bond with host bone..

Nurazreena Ahmad, Kami Tsuru, Melvin L. Munar, Shigeki Matsuya, Kunio Ishikawa, Effect of precursor solubility on the mechanical strength of HAp block, Advances in Bioceramics and Porous Ceramics V - 36th International Conference on Advanced Ceramics and Composites, ICACC 2012, 2013.04, The effect of the solubility of the precursors, alpha tricalcium phosphate (α-TCP) and beta tricalcium phosphate (β-TCP) on the mechanical property of hydroxyapatite (HAp) bone substitute was investigated. Uniaxially pressed compacts starting from these precursors were treated hydrothermally with 1 mol/L of ammonia solution at 200°C for various durations. XRD analysis revealed that α-TCP took 3 hours whereas β-TCP took 240 hours for complete transformation to HAp. The porosity of HAp block obtained from β-TCP was found to be lower than that of HAp block from α-TCP. Diametral tensile strength of HAp block from β-TCP showed a significantly higher value than that of HAp block obtained from α-TCP. It is therefore concluded that solubility of precursor affects the mechanical strength of the HAp block..

Arief Cahyanto, Michito Maruta, Kanji Tsuru, Shigeki Matsuya, Kunio Ishikawa, Basic properties of carbonate apatite cement consisting of vaterite and dicalcium phosphate anhydrous, 24th Symposium and Annual Meeting of International Society for Ceramics in Medicine, ISCM 2012, 2013, The aim of the present study is to fabricate bone cement that could transform to carbonate apatite (CO3Ap) completely at body temperature. The powder phase of vaterite and dicalcium phosphate anhydrous (DCPA) was mixed with 0.8 mol/L of NaH2PO4, Na 2HPO4, and Na3PO4 aqueous solution, respectively, with liquid to powder ratio (L/P ratio) of 0.45, 0.55, and 0.65. The paste was packed into split stainless steel mold, covered with the glass slide and kept at 37°C and 100% relative humidity for up to 96 hours (h). XRD analysis revealed that the cement became pure CO3Ap within 24 h for Na3PO4, 72 h for Na2HPO4, and 96 h for NaH2PO4, respectively. FT-IR results showed that all of the obtained specimens could be assigned to B-type CO3Ap. CHN analysis showed the carbonate content of the specimen were 10.4 ± 0.3% for NaH2PO4, 11.3 ± 0.7% for Na2HPO 4, and 11.8 ± 0.4% for Na3PO4, respectively. Diametral tensile strength of the set CO3Ap cement was 1.95 ± 0.42 MPa for NaH2PO4, 2.53 ± 0.53 MPa for Na2HPO4, and 3.45 ± 1.53 MPa for Na 3PO4, respectively. The set CO3Ap cement had low crystallinity similar to bone apatite since it was synthesized at body temperature. We concluded, therefore, that CO3Ap cement prepared from the present method has higher possibility to be used as an ideal bone replacement..

92.

Daiki Honda, Akari Takeuchi, Kunio Ishikawa, Basic properties of starfish derived calcium carbonate and its phase transformation to carbonate apatite, 24th Symposium and Annual Meeting of International Society for Ceramics in Medicine, ISCM 2012, 2013, Feasibility of starfish bone to be a source material for apatite bone substitute was investigated in the present study because starfish bone is known to be porous calcium carbonate. Starfish bone was assembly of Mg containing calcite granules. And the calcite granules had fully interconnected porous structure with approximately 20 μm of pore size. After the hydrothermal treatment of the calcite granules in Na2HPO4aqueous solution, the granules were gradually transformed to apatite. Therefore, starfish derived calcium carbonate would be a candidate of a source material for carbonate apatite bone substitute..

93.

Arief Cahyanto, Kanji Tsuru, Kunio Ishikawa, Carbonate apatite formation during the setting reaction of apatite cement, Advances in Bioceramics and Porous Ceramics V - 36th International Conference on Advanced Ceramics and Composites, ICACC 2012, 2013, Replacement of apatite cement (AC) to bone is still controversial issue. To understand factor that could affect the replacement of AC to bone, AC consisting of an equimolar mixture of tetracalcium phosphate (TTCP; Ca 4(PO4)2O) and dicalcium phosphate anhydrous (DCPA; CaHPO4) was allowed to set at 37°C and 100% relative humidity under 5% CO2 or N2. Carbonate apatite (CO 3Ap) was formed when AC was allowed to set under 5% CO2. The amount of CO3 decreased gradually as the depth from the surface increased. The CO3Ap was the B-type CO3Ap in which CO 32- was replaced with PO43- and the CO3Ap found in bone. Larger amount of TTCP remain unreacted when the AC was allowed to set under N2 whereas smaller amount of TTCP remain unreacted when the AC was allowed to set under CO2. This may be caused by the larger Ca/P molar ratio of CO3Ap. Formation of CO 3Ap and/or small unreacted TTCP are thought to be key factors for the replacement of AC to bone..

94.

Girlie M. Munar, Melvin L. Munar, Kanji Tsuru, Kunio Ishikawa, Comparison of PLGA reinforcement method for carbonate apatite foam, 24th Symposium and Annual Meeting of International Society for Ceramics in Medicine, ISCM 2012, 2013, Carbonate apatite (CO3Ap) foam with interconnecting porous structure is a potential candidate as bone substitute material owing to its similarity to the cancellous bone with respect to composition, morphology and osteoclastic degradation. However, it is brittle and difficult to handle. This is thought to be caused by no organic material in the CO3Ap foam. The aim of this study is to reinforce the CO3Ap foam with poly(DL-lactide-co-glycolide) (PLGA). Immersion and vacuum infiltration methods were compared as reinforcing methods. Compressive strength of unreinforced CO3Ap foam, (12.0 ± 4.9 kPa) increased after PLGA reinforcement by immersion (187.6 ± 57.6 kPa) or by vacuum infiltration (407 ± 111.4 kPa). Scanning electron microscopy (SEM) showed the preservation of full interconnecting porous structure of CO3Ap foam after PLGA reinforcement using immersion or vacuum infiltration. Interface between the PLGA and CO3Ap foam, however revealed that no gap was found between the PLGA and CO3Ap foam interface when vacuum was used to reinforce the PLGA whereas a gap was found when simple immersion was used. Strong interface between PLGA and CO3Ap foam is therefore thought to be the key for higher compressive strength. In conclusion, vacuum infiltration is a more efficient method to reinforce the CO3Ap foam with PLGA for improving the mechanical strength without sacrificing the cancellous bone-type morphology..

95.

Xingling Shi, Kanji Tsuru, Giichiro Kawachi, Kunio Ishikawa, Effects of hydrothermal treatment on properties of titanium nitride coating for dental implants, 24th Symposium and Annual Meeting of International Society for Ceramics in Medicine, ISCM 2012, 2013, To improve surface hardness of dental implant made of pure titanium (Ti), titanium nitride (TiN) coating was introduced. However, studies revealed that TiN only showed osseointegration similar or inferior to that of Ti. Therefore it is necessary to improve the biocompatibility of TiN for dental implant coating. In the present study, TiN coating was prepared on pure Ti substrates and hydrothermal treatment was conducted to modify its surface properties. It was found that, TiN surface was partially oxidized after treatment and calcium (Ca) was successfully combined onto its surface. Surface morphology, roughness and hardness were not affected after treatments below 140°C and wettability was obviously improved..

96.

Tram Nguyen Xuan Thanh, Michito Maruta, Kanji Tsuru, Alireza Valanezhad, Shigeki Matsuya, Kunio Ishikawa, Fabrication of calcite foam by inverse ceramic foam method, 24th Symposium and Annual Meeting of International Society for Ceramics in Medicine, ISCM 2012, 2013, We have previously reported that calcite foam that had interconnected porous structure could be prepared by ceramic foam method and it transformed to carbonate apatite (CO3Ap). In the ceramic foam method, polyurethane sponge was used as a template. The polyurethane sponge was immersed in the ceramics slurry, and the strut of the polyurethane foam was covered by ceramic powder. After that it was dried and sintered at high temperature. Calcite foams produced by this approach were comprised of a three-dimensional (3D) interconnected porous structure that facilitated cell penetration. However, all foams have a common limitation: the inherent lack of mechanical strength associated with high porosity. Therefore, in this study, an inverse ceramic foam method was studied; multi polyurethane coating method using polyurethane foam as a template. In this study, the compressive strength was improved by an inverse replication allowed for decreasing porosity while at the same time maintaining the interconnectivity. The burnable synthetic resin coating layer was introduced onto struts of polyurethane foam to make the triangular struts become more round and thick, consequently producing large round capillary within the foam structure fulfilling the requirement for osteoblast colonization. In particular, polyurethane foam was dipped orderly into two monomers, followed by centrifugation to remove excess liquids inside foam. After resin curing, a layer of synthetic resin was coated strut of foam. Calcium hydroxide Ca(OH) 2 slurry was then infiltrated into resin coated-polyurethane foam. By firing at 600°C in O2-CO2 stream, polyurethane template was burnt off and Ca(OH)2 was converted into calcite. Negative replicated calcite foam was fabricated and characterized micro-structurally with interconnectivity and improved mechanical strength. The results obtained in this study suggested that this method dramatically improved the mechanical strength of the calcite foam without sacrificing the interconnected structure, and this means that the calcite foam obtained in this method could be precursors for the 3D interconnected porous CO3Ap foam..

97.

Girlie M. Munar, Melvin L. Munar, Kanji Tsuru, Shigeki Matsuya, Kunio Ishikawa, Fabrication of carbonate apatite-PLGA hybrid foam bone substitute, Advances in Bioceramics and Porous Ceramics V - 36th International Conference on Advanced Ceramics and Composites, ICACC 2012, 2013, Porous carbonate apatite (CO3AP) foam is a potential bone substitute material since it approximates the morphology and mineral phase of bone. One drawback however, is the poor mechanical properties for sufficient handling. A useful method to improve the mechanical property is by reinforcing it with biodegradable polymer. This study reports the preparation of carbonate apatite-PLGA (CO3AP-PLGA) hybrid foam with improved mechanical strength and osteoconductivity. CO3AP foam was prepared by hydrothermal treatment of α-tricalcium phosphate (αTCP) foam in carbonate solution at 150°C for 24 hours. CO3AP powder was synthesized from vaterite (CaCO3) and disodium hydrogen phosphate (Na2HPO4) aqueous solution at 37°C. The obtained CO3AP powder was mixed with 10wt% PLGA solution then reinforced on CO3AP foam using freeze-vacuum technique. The obtained CO 3AP-PLGA hybrid foam showed interconnecting porous structure with average porosity of 85%. Compressive strength of CO3Ap-PLGA hybrid foam was as high as 0.35 MPa when compared to that of CO3Ap foam at 0.01 MPa. X-ray diffraction and FT-IR showed CO3Ap as the primary mineral phase. In conclusion, CO3AP-PLGA hybrid foam with improved mechanical properties and approximates the mineral composition and morphology of the cancellous bone can be a potential bone substitute or scaffold for tissue engineering..

98.

Shunsuke Nomura, Kanji Tsuru, Shigeki Matsuya, Ichiro Takahashi, Kunio Ishikawa, Fabrication of spherical carbonate apatite using calcium sulfate as a precursor by W/O emulsion method, 24th Symposium and Annual Meeting of International Society for Ceramics in Medicine, ISCM 2012, 2013, We fabricated spherical carbonate apatite from spherical calcium sulfate which was prepared by water-in-oil emulsion method. Calcium sulfate hemihydrate slurry was dropped in oil under continuous stirring and was kept at room temperature for 60 min to obtain set spherical calcium sulfate dihydrate (CaSO4·2H2O) with approximately 1 mm in diameter. The spherical CaSO4·2H2O was hydrothermally-treated at 120°C for 24 hours in the presence of 0.4 mol.L-1 disodium hydrogen phosphate and sodium hydrogen carbonate aqueous solution. X-ray diffraction patterns assigned to apatite single phase could be detected from the obtained spheres. Carbonate content in apatitic structure was found to be approximately 6.5wt%..

99.

Taro Nikaido, Kanji Tsuru, Giichiro Kawachi, Melvin Munar, Shigeki Matsuya, Seiji Nakamura, Kunio Ishikawa, Fabrication of βTCP foam using αTCP foam as a precursor by heat treatment, 24th Symposium and Annual Meeting of International Society for Ceramics in Medicine, ISCM 2012, 2013, The present study reports the synthesis of βTCP foam with fully interconnecting pores based on phase transformation of αTCP foam precursor by employing heat treatment. First, the αTCP foam precursor was fabricated by sintering the ceramics slurry-coated polyurethane foam template at 1,500°C. The resultant αTCP foam was again heated below α,βtransition temperature for an extended period of times. After heating at 800°C for 150 hours, 900°C for 100 hours and 1,000°C for 300 hours, βTCP foam was obtained. The compressive strength of βTCP foam was approximately 46 kPa and the porosity was approximately 93%. The long heating period as well as heating temperature were the key to the transformation of βTCP phase. βTCP foam could be an ideal bone replacement since the invasion of bone cells into the pores provides optimum bone growth or repair..

100.

Michito Maruta, Shigeki Matsuya, Kanji Tsuru, Kunio Ishikawa, Improvement in handling property of αTCP cement, 24th Symposium and Annual Meeting of International Society for Ceramics in Medicine, ISCM 2012, 2013, This study aims to improve the handling property of alpha-tricalcium (αTCP) cement. In order to improve the handling property, the effect of γ-poly-glutamic acid (γPGA) as a chelating agent was studied. γPGA is water soluble, biodegradable, nontoxic, and edible material. γPGA contains carboxyl group, so the chelating effect between Ca 2+ ions released from calcium phosphate cement and carboxyl group of γPGA is prospected when it mixed with αTCP based cement. The results obtained in this study clearly demonstrated that the addition of γPGA into the αTCP cement was highly effective in controlling the handling property of αTCP cement..

101.

Shigeki Matsuya, Michito Maruta, Kanji Tsuru, Kunio Ishikawa, Preparation of carbonate apatite cement based on α-TCP, 24th Symposium and Annual Meeting of International Society for Ceramics in Medicine, ISCM 2012, 2013, Carbonate apatite showed an excellent bioresorbability through the remodeling process of bone. In the present study, we prepared self-setting carbonate apatite cement based on α-TCP. We tried two types of the cement powder formulations, that is, first one (F1) is α-TCP containing given amounts (10 to 50 mass%) of synthesized carbonate apatite and second one (F2) is α-TCP treated in 0.5M NaHCO3 for various times between 90 and 360 min. The cement powder was mixed with 0.25M Na2HPO4 to allow set at 37°C and 100% of relative humidity up to 1 day. XRD and FT-IR results showed formation of B-type carbonate apatite phase after setting in both of the formulations. With the formulation, F1, the carbonate content was increased with the treatment time and the maximum content was 4.1 mass%. DTS deacreased with the amount of cabonate apatite in the formulation, F1, however, it increased up to 9 MPa with treatment time in the formulation, F2..

Shunsuke Nomura, Kanji Tsuru, Alireza Valanezhad, Shigeki Matsuya, Ichiro Takahashi, Kunio Ishikawa, Fabrication of carbonate apatite block from calcium sulfate by hydrothermal treatment, 23rd Symposium and Annual Meeting of International Society for Ceramics in Medicine, ISCM 2011, 2012.01, Carbonate apatite (CO3Ap) is expected to be an ideal bone substitute since it can harmonize with the bone remodeling cycle. The aim of this study is to fabricate a CO3Ap bone substitute from gypsum (calcium sulfate, CaSO4·2H2O) hardening bodies based on dissolution-precipitation reaction. Calcium sulfate hemihydrate mixed with water at a water-to-powder ratio of 0.5 was packed in a split stainless mold and kept at room temperature for 24 hours to obtain set CaSO 4·2H2O. The set CaSO4·2H 2O was hydrothermally treated in the presence of disodium hydrogen phosphate (Na2HPO4) and sodium hydrogen carbonate (NaHCO3). The results of powder X-ray diffraction and Fourier transform infrared spectroscopy indicated that CO3Ap block could be fabricated from the set CaSO4·2H2O block by hydrothermal treatment with Na2HPO4 and NaHCO3. When the treatment temperature was increased, the conversion rate to CO 3Ap increased. However, the carbonate content decreased with increasing treatment temperature..

110.

Aireza Valanezhad, Kanji Tsuru, Michito Maruta, Shigeki Matsuya, Kunio Ishikawa, A novel HAp coating method on titanium, 23rd Symposium and Annual Meeting of International Society for Ceramics in Medicine, ISCM 2011, 2012, A coating layer with hierarchical structure: Titanium-Zinc-Phosphate (Ti-Zn-PO4) / Hydroxyapatite (HAp) coating layer was prepared on titanium (Ti). The Ti plates were treated using two step hydrothermal treatments: first step in acidic zinc phosphate solution to form Ti-Zn-PO 4 coating and second step in calcium chloride solution to form HAp. The Ti-Zn-PO4 layer strongly attached to the Ti surface. The adhesive strength of the coating layer was measured higher than 48 MPa. The surface observation and element analysis indicated that the Ti plates were covered with Ti-Zn-PO4 coating layer after hydrothermal treatment at 250°C. When Ti-Zn-PO4 coating was treated hydrothermally with calcium chloride solution, crystalline HAp layer was formed on its surface..

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Kanji Tsuru, Akihiro Otsu, Michito Maruta, Alireza Valanezhad, Giichiro Kawachi, Akari Takeuchi, Shigeki Matsuya, Kunio Ishikawa, Calcite bone substitute prepared from calcium hydroxide compact using heat-treatment under carbon dioxide atmosphere, 23rd Symposium and Annual Meeting of International Society for Ceramics in Medicine, ISCM 2011, 2012, The purpose of this study is to investigate whether calcite blocks with high mechanical property could be obtained for a short period from calcium hydroxide (Ca(OH)2) compact using heat-treatment under carbon dioxide (CO2) atmosphere. The Ca(OH)2 disks compacted with different pressure was heated at different temperature ranging from 200°C to 800°C for an hour under CO2 atmosphere. From the X-ray diffractometry, Ca(OH)2 converted into calcite along with the rise of the heating temperature. Small amount of unreacted Ca(OH)2 remained in samples heated at 600°C whereas samples treated at 800°C converted to calcite with very small amount of calcium oxide. The diametral tensile strength (DTS) value increased with the rise of heating temperature up to 600°C then decreased down to 800°C. Meanwhile, the porosity decreased with the rise of heating temperature up to 600°C then slightly increased up to 800°C. From the scanning electron microscope observation, grains grew bigger along with the rise of heating temperature. Intergranular space between grains decreased from 200°C to 600°C. The highest DTS value (14 MPa±1.3) at 600°C could be the result of lesser intergranular space due to sintering..

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Taro Nikaido, Kanji Tsuru, Fumikazu Daitou, Melvin Munar, Shigeki Matsuya, Seiji Nakamura, Kunio Ishikawa, Fabrication of βtcp with fully-interconnected porous structure, 23rd Symposium and Annual Meeting of International Society for Ceramics in Medicine, ISCM 2011, 2012, Calcium phosphate foam could be an ideal bone filler and scaffold for tissue engineering. This paper describes fabrication method of β-tricalcium phosphate (βTCP) foam with fully-interconnected porous structure by employing magnesium oxide (MgO) as βTCP stabilizer. The foam was prepared using the so-called ceramics foam method. MgO was added to calcium carbonate and dicalcium phosphate dihydrate so that 0, 1, 2, 3, 4, 6 and 8 mol% calcium would be substituted by magnesium (Mg) in βTCP structure. After sintering at 1500°C, crystal phase of the obtained foam included β-tricalcium phosphate (αTCP) when no Mg or less than 3 mol% Mg was added. In contrast, crystal phase was single phase βTCP when 3 mol% or higher Mg was added. The compressive strength was approximately 15 kPa and the porosity was above 95% for all specimens. No significant difference was observed between αTCP and βTCP foams in compressive strength and porosity when the sintering temperature was the same..

113.

Kunio Ishikawa, Kanji Tsuru, Trung Kien Pham, Michito Maruta, Shigeki Matsuya, Fully-interconnected pore forming calcium phosphate cement, 23rd Symposium and Annual Meeting of International Society for Ceramics in Medicine, ISCM 2011, 2012, Calcium phosphate cement that foams fully-interconnected porous structure along with its gradual replacement to bone may be ideal for bone defect reconstruction. In the present study, α-tricalcium phosphate (αTCP) microspheres were exposed to acidic calcium phosphate solution. It was found that the αTCP microspheres set in approximately 10 min to form fully-interconnected porous structure. The porosity was approximately 50% and the pore size was 300μm. The surface of the porous body was dicalcium phosphate dihydrate whereas the inside was αTCP..

L. J. Cardenas, A. Takeuchi, K. Tsuru, S. Matsuya, Kunio Ishikawa, Synthesis and in vitro cell compatibility of α-tricalcium phosphate-based apatite cement containing tricalcium silicate, 3rd International Conference on the Development of Biomedical Engineering in Vietnam, 2010, The presence of silicate in artificial bone graft material is known to be effective in increasing bone formation rate. We previously reported the basic setting properties of α-tricalcium phosphate (α-Ca 3PO4; α-TCP) based apatite cement (AC) with various amount of tricalcium silicate (Ca3SiO5; alite) addition using sodium dihydrogen phosphate (NaH2PO4) as the liquid phase. In this study, in vitro biological compatibility of pure α-TCP and 2.5-10.0 wt% alite added to α-TCP based AC is investigated in terms of cell attachment, proliferation and differentiation. Set ACs aged for 168 hrs were used for cell studies with bone marrow cells from tibia of 4 week-old, male, SD rat. Initial cell attachment was observed after 7 hrs; cell proliferation was observed after 3, 5, and 7 days. Cell differentiation (alkaline phosphatase activity) was observed after 3, 6, and 9 days of incubation. Cell attachment of alite added ACs were almost the same as sintered hydroxyapatite (HAp) and alite-free AC. Cell proliferation at 2.5-7.5 wt% alite added ACs were significantly higher at day 5 and 7 (p<0.05). Alkaline phosphatase activity revealed that 2.5 wt% alite addition accelerated the osteogenic cell activity at day 6 and 9 (p<0.05) whereas too much alite addition resulted in the decrease of osteogenic cell activity. In conclusion, we found that α-TCP based AC containing appropriate amount of alite could be an improved AC since it shows suitable setting time, higher mechanical strength and possible higher osteoconductivity..

A. Kawasaki, T. Suge, Kunio Ishikawa, T. Matsuo, Effects of ammonium hexafluorosilicate on acid resistance of enamel and dentin, Transactions - 7th World Biomaterials Congress, 2004, The effects of ammonium hexafluorosilicate on the acid resistance of bovine enamel and dentin were analyzed. In the case of enamel specimens, shallower demineralized depth was found when the enamel specimens were treated with ammonium hexafluorosilicate or damine silver fluoride. It was also observed that all the fluoride solutions had abilities to reduce the demineralized depth in the case of dentin specimens. The result shows that ammonium hexafluorosilicate is useful to prevent enamel and dentin caries since ammonium hexafluorosilicate treatment increases acid resistance of enamel and dentin to the same degree with diamine silver fluoride without changing the tooth color..

120.

Kunio Ishikawa, S. Matsuya, X. Lin, K. Udoh, Masaharu Nakagawa, Y. Terada, Fabrication of carbonate apatite monolith from calcium carbonate with ammonium hydrogen phosphate treatment, Transactions - 7th World Biomaterials Congress, 2004, The feasibility of preparing carbonate apatite monolith from calcium hydroxide powder, carbon dioxide and ammonium hydrogen phosphate was evaluated. It was observed that carbonate apatite was the most stable phase thermodynamically when calcium, phosphate and carbonate ions were present. The coralline apatite was prepared by the hydrothermal treatment of coral that was aragonite in the presence of phosphate ions. The method was found to allow the formation carbonate apatite with good carbonate content, and with similar crystallinity to that of human bone..

121.

T. Suge, A. Kawasaki, Kunio Ishikawa, T. Matsuo, Occlusion of dentinal tubules with ammonium hexafluorosilicate for treatment of dentin hypersensitivity, Transactions - 7th World Biomaterials Congress, 2004, The possibility of using ammonium hexafluorosilicate for the treatment of dentin hypersensitivity was investigated. The occluding ability of dentinal tubules with ammonium hexafluorosilicate was evaluated in vitro using human extracted teeth. Scanning electron microscopy revealed that dentinal tubules were occluded homogeneously with precipitate after treatment with ammonium hexafluorosilicate. It was found that the amount of the precipitate formed in dentinal tubules was slightly smaller when the dentinal tubules were enlarged with 6% or 50% citric acid when compared with other groups..